Computer Literacy Advanced: Networking, Cybersecurity, Cloud Computing & AI for PSC

Advanced computer literacy questions appear in most PSC exams — typically 3-6 questions covering networking, internet, cybersecurity, and emerging technologies. This note focuses on the factual content examiners test.

Computer Networks — Types

Network Type	Full Form	Range	Example
PAN	Personal Area Network	~10 meters	Bluetooth between phone and earbuds
LAN	Local Area Network	Building/campus (up to ~1 km)	Office network, school computer lab
MAN	Metropolitan Area Network	City-wide (~50-100 km)	Cable TV network; city-wide Wi-Fi
WAN	Wide Area Network	Country/continent/global	Internet is the largest WAN
WLAN	Wireless LAN	Same as LAN but wireless	Wi-Fi network
VPN	Virtual Private Network	Over internet	Secure remote access to office network

Network Topologies

Topology	Description	Advantage
Bus	All devices on a single cable	Simple; cheap
Star	All devices connect to a central hub/switch	Most common; one failure doesn’t affect others
Ring	Devices in a circular loop	Equal access; no collision
Mesh	Every device connects to every other	Most reliable; redundant; expensive
Tree	Hierarchical; combination of star and bus	Scalable

Network Devices

Device	Function
Hub	Broadcasts data to all ports; no intelligence; Layer 1
Switch	Sends data only to intended device (MAC address); Layer 2
Router	Connects different networks; uses IP addresses; Layer 3
Modem	Converts digital to analog (and vice versa) for internet over phone lines
Gateway	Connects two different types of networks
Firewall	Filters incoming/outgoing traffic; security device
Bridge	Connects two LANs of the same type
Access Point	Provides wireless connectivity to a wired network

Internet Protocols

Protocol	Full Form	Function
TCP/IP	Transmission Control Protocol / Internet Protocol	Foundation of internet; ensures reliable data delivery
HTTP	HyperText Transfer Protocol	Web page transfer (unsecured)
HTTPS	HTTP Secure	Encrypted web transfer (uses SSL/TLS)
FTP	File Transfer Protocol	File upload/download between computers
SMTP	Simple Mail Transfer Protocol	Sending emails
POP3	Post Office Protocol v3	Receiving emails (downloads to device)
IMAP	Internet Message Access Protocol	Receiving emails (keeps on server)
DNS	Domain Name System	Converts domain names to IP addresses; “phonebook of the internet”
DHCP	Dynamic Host Configuration Protocol	Automatically assigns IP addresses
SSH	Secure Shell	Secure remote login
Telnet	—	Remote login (unsecured)
VoIP	Voice over Internet Protocol	Phone calls over internet (Skype, WhatsApp calls)
IP	Internet Protocol	Addressing and routing; IPv4 (32-bit) and IPv6 (128-bit)

IP Addressing

Version	Bits	Format	Example	Addresses
IPv4	32-bit	Decimal (4 octets)	192.168.1.1	~4.3 billion
IPv6	128-bit	Hexadecimal (8 groups)	2001:0db8:85a3::8a2e	~340 undecillion (virtually unlimited)

OSI Model (7 Layers)

Layer	Name	Function	Protocol/Device
7	Application	User interface; software	HTTP, FTP, SMTP, DNS
6	Presentation	Data format, encryption	SSL, JPEG, GIF
5	Session	Session management	NetBIOS
4	Transport	Reliable delivery; error check	TCP, UDP
3	Network	Routing; IP addressing	IP; Router
2	Data Link	MAC addressing; framing	Switch, Bridge
1	Physical	Hardware; cables; signals	Hub, Cable, NIC

Mnemonic (top to bottom): “All People Seem To Need Data Processing” = Application, Presentation, Session, Transport, Network, Data Link, Physical.

Cybersecurity

Types of Cyber Threats

Threat	Description
Virus	Malicious program that attaches to files; needs human action to spread
Worm	Self-replicating; spreads without human action; exploits network vulnerabilities
Trojan Horse	Disguised as legitimate software; does not self-replicate
Ransomware	Encrypts victim’s data; demands ransom for decryption key (e.g., WannaCry, 2017)
Phishing	Fake emails/websites to steal credentials; social engineering attack
Spyware	Secretly monitors user activity
Adware	Displays unwanted advertisements
Keylogger	Records keystrokes to steal passwords
DDoS	Distributed Denial of Service; floods server with traffic to crash it
Man-in-the-Middle	Attacker intercepts communication between two parties
SQL Injection	Inserts malicious SQL code into database queries
Zero-day attack	Exploits unknown vulnerability before patch is available

Security Measures

Measure	Function
Firewall	Filters network traffic; blocks unauthorized access
Antivirus	Detects and removes malware
Encryption	Converts data into unreadable code; only decrypted with key
SSL/TLS	Secure Sockets Layer / Transport Layer Security; encrypts web traffic (HTTPS)
Two-Factor Authentication (2FA)	Two forms of identity verification (password + OTP)
Biometric security	Fingerprint, iris scan, face recognition
Digital Signature	Verifies identity and integrity of digital documents
Digital Certificate	Issued by Certificate Authority (CA); authenticates website identity

Important Cybersecurity Terms

Term	Meaning
Hacker	White hat (ethical), Black hat (criminal), Grey hat (mixed)
CERT-In	Indian Computer Emergency Response Team; under MeitY; handles cyber incidents
Cyber crime	In India governed by IT Act, 2000 (amended 2008)
Dark Web	Part of internet not indexed by search engines; accessed via Tor browser
Cookie	Small text file stored by websites on user’s browser
Cache	Temporary storage of frequently accessed data for faster retrieval

Cloud Computing

Concept	Detail
Definition	Delivery of computing services (servers, storage, databases, networking, software) over the internet (“the cloud”)
On-demand	Pay-as-you-use; no upfront hardware investment

Service Models

Model	Full Form	What You Get	Example
IaaS	Infrastructure as a Service	Virtual machines, storage, networking	Amazon AWS EC2, Google Compute
PaaS	Platform as a Service	Development platform; OS + tools	Google App Engine, Heroku
SaaS	Software as a Service	Ready-to-use software via browser	Gmail, Google Docs, Zoom, Microsoft 365

Mnemonic: “I Pizza Slice” — IaaS = raw ingredients, PaaS = kitchen to cook, SaaS = delivered pizza.

Deployment Models

Model	Description
Public Cloud	Shared infrastructure; available to anyone (AWS, Azure, Google Cloud)
Private Cloud	Dedicated to one organization
Hybrid Cloud	Combination of public and private
Community Cloud	Shared by organizations with common concerns

Major Cloud Providers

Provider	Company
AWS	Amazon (market leader)
Azure	Microsoft
Google Cloud (GCP)	Google
MeghRaj	Indian government cloud initiative (GI Cloud)

Artificial Intelligence (AI) Basics

Concept	Definition
AI	Machines that simulate human intelligence — learning, reasoning, problem-solving
Machine Learning (ML)	Subset of AI; systems learn from data without explicit programming
Deep Learning	Subset of ML; uses neural networks with many layers
Natural Language Processing (NLP)	AI that understands and generates human language (e.g., chatbots, translation)
Computer Vision	AI that interprets images and videos
Robotics	Machines performing tasks autonomously or semi-autonomously
Neural Network	Computing system inspired by human brain; nodes (neurons) in layers

AI Milestones

Event	Year	Detail
Term “Artificial Intelligence” coined	1956	John McCarthy at Dartmouth Conference
Deep Blue beats Kasparov	1997	IBM’s chess computer
Watson wins Jeopardy!	2011	IBM’s NLP system
AlphaGo beats Go champion	2016	Google DeepMind
ChatGPT released	2022	OpenAI; generative AI chatbot
Turing Test	1950 (proposed)	Alan Turing; test if machine can exhibit human-like intelligence

Types of AI

Type	Description	Example
Narrow/Weak AI	Designed for specific tasks	Siri, Alexa, Google Assistant, chess engines
General/Strong AI	Human-level intelligence across all tasks	Does not exist yet
Super AI	Surpasses human intelligence	Theoretical concept

Emerging Technologies — Quick Facts

Technology	Key Fact
Blockchain	Decentralized digital ledger; basis of cryptocurrencies; tamper-proof
IoT (Internet of Things)	Network of physical devices connected to internet; smart homes, wearables
5G	Fifth generation mobile network; ~10 Gbps speed; low latency
Big Data	Extremely large datasets; characterized by 3Vs — Volume, Velocity, Variety
Quantum Computing	Uses qubits (can be 0, 1, or both simultaneously); exponentially faster for certain problems
Cryptocurrency	Digital currency using blockchain; Bitcoin (2009, Satoshi Nakamoto) is the first
NFT	Non-Fungible Token; unique digital asset on blockchain

Quick Recall

1. Internet is what type of network? → WAN
2. DNS does what? → Converts domain names to IP addresses
3. SMTP is used for? → Sending emails
4. IPv4 uses how many bits? → 32 bits
5. OSI model has how many layers? → 7
6. WannaCry is what type of attack? → Ransomware
7. IT Act of India? → 2000 (amended 2008)
8. SaaS example? → Gmail, Google Docs
9. Father of AI? → John McCarthy
10. Blockchain is the basis of? → Cryptocurrency (Bitcoin)